SAN DIEGO — Southern California teenager Zac Sunderland sailed back into U.S. waters in the middle of the night and was soon enjoying chocolate cake and room service.

He’s already thinking about his next adventure, even as he prepares to finish this one.

The 17-year-old Sunderland has about 100 miles to go to become the youngest person to sail around the world alone. He’s due in Marina del Rey, in the Los Angeles area, at 10 a.m. PDT Thursday, 13 months and two days after he left.

“It’s all but over right now,” Sunderland said late Monday morning. “I’d do it again in a heartbeat. It’s been an amazing year. Tons of fun, lots of great stuff.”

Sunderland pulled into San Diego overnight aboard his 36-foot boat, Intrepid. He cleared customs — “It’s good; I’m in,” he said — and had to get his engine repaired. He uses it for going into and out of ports, and in case of emergencies.

“It doesn’t really matter, but I’d rather not get towed into the harbor that you finish in,” he said with a laugh.

The shaggy-haired Sunderland, who’s from Thousand Oaks, northwest of L.A., hoped to be under way again by Monday afternoon. He might pull into a small harbor between San Diego and Los Angeles for a day or two so he can perfectly time his arrival.

Sunderland was 16 when he left Marina Del Rey on June 14, 2008.

His total trip is estimated at 28,000 miles.

“A big circle,” he said.

Along the way he encountered a boat full of pirates and severe storm damage. He also had few enjoyable times such as surfing while waiting for his boat to be repaired on an island in the Indian Ocean.

“I don’t know what to think right now,” he said. “It’s kind of crazy with this whole yearlong endeavor drawing to a close. It’ll be awesome to see my friends, have a little bit of summer left. I’m still figuring out what’s going on next.”

He was met on his arrival in San Diego by his father, Laurence, a younger brother and a friend who brought “a massive hunk of chocolate cake. It was probably a foot and a half long. We gorged on that, got room service. We had a good night.”

Sunderland’s progress up the Mexican coast was slowed by wind, current and a cracked bulkhead that forced him into port for repairs. His father is a shipwright and has met him at various stops around the world.

Sunderland turns 18 on Nov. 29. The record for the youngest solo circumnavigation is held by an Australian who was 18 years, 41 days when he completed his voyage in 1996.

Also trying for the record is 17-year-old British sailor Mike Perham, who is a few months younger than Sunderland and sailing a bigger, faster boat. Perham has had breakdowns and had been forced to stop in New Zealand for repairs, but could supplant Sunderland in the record book.

Sunderland said he’d like to climb Mount Everest.

“I love adventure,” he said. “I want to do some more research on it see if I can make that happen and see if I can do it without a guide.”